1. Field of the Invention
The present invention generally relates to touchscreen panels, electronic apparatuses having touchscreen panels, and methods of fabricating touchscreen panels.
2. Description of the Related Art
The touchscreen panel is arranged in front of a display panel, and is used as an input device to detect the presence and location of a touch on a display of the display panel. Because the touchscreen panel enables a user to make a direct input based on information that is displayed on the display panel and is visually detected by the user, the touchscreen panel is popularly used in various applications.
A resistive touchscreen panel is well known. The resistive touchscreen panel has an upper electrode substrate formed with a transparent conductor layer, and a lower electrode substrate formed with a transparent conductor layer, with a gap formed between the opposing transparent conductor layers. When a force is applied at one point on the upper electrode substrate, the opposing transparent conductor layers make contact to enable detection of the position where the force is applied.
The resistive touchscreen panel may be roughly categorized into the 4-wire type and the 5-wire type. The 4-wire type resistive touchscreen panel has an x-axis electrode provided on one of the upper and lower electrode substrates, and a y-axis electrode provided on the other of the upper and lower electrode substrates. On the other hand, the 5-wire type resistive touchscreen panel has both the x-axis electrode and the y-axis electrode provided on the lower electrode substrate, and the upper electrode substrate functions as a probe for detecting a voltage.
The applicants are aware of Japanese Laid-Open Patent Publications No. 2004-272722 and No. 2008-293129.
Next, a description will be given of the 5-wire resistive touchscreen panel, by referring to FIGS. 1 and 2. FIG. 1 is a perspective view illustrating an example of the 5-wire resistive touchscreen panel, and FIG. 2 is a cross sectional view illustrating the 5-wire resistive touchscreen panel of FIG. 1.
As illustrated in FIGS. 1 and 2, a 5-wire resistive touchscreen panel 200 has a film 210 forming an upper electrode substrate, a transparent conductor layer 230 formed on one surface of the film 210, a glass 220 forming a lower electrode substrate, a transparent conductor layer 240 formed on one surface of the glass 220, and a spacer 250 sandwiched between the two mutually opposing transparent conductor layers 230 and 240. The 5-wire resistive touchscreen panel 200 may be electrically connected to a host computer (not illustrated) via a cable 260.
FIGS. 3A and 3B respectively are a perspective view and a circuit diagram for explaining a coordinate detection in the 5-wire resistive touchscreen panel 200. A voltage is alternately applied in the x-axis direction and in the y-axis direction via electrodes 241, 242, 243 and 244 that are provided at end portions of the four sides of the transparent conductor layer 240 as illustrated in FIG. 3A. When the transparent conductor layers 230 and 240 make contact at a contact position A that is pressed by a finger tip F of the user, for example, a potential Va is detected via the transparent conductor layer 230 as illustrated in FIG. 3B, in order to detect coordinate positions in the x-axis direction and the y-axis direction. In FIG. 3B, Rw denotes a wiring resistance, and IN denotes an input area of the transparent conductor layer 240.
However, the 5-wire resistive touchscreen panel 200 can only detect a single contact position at one time. If multiple contact positions are pressed simultaneously by the finger tips F of the user, for example, the 5-wire resistive touchscreen panel 200 cannot detect the multiple contact positions that are pressed simultaneously.
FIGS. 4A and 4B respectively are a perspective view and a circuit diagram for explaining the coordinate detection in the 5-wire resistive touchscreen panel when multiple contact positions occur simultaneously. In FIGS. 4A and 4B, those parts that are the same as those corresponding parts in FIGS. 3A and 3B are designated by the same reference numerals, and a description thereof will be omitted.
A voltage is alternately applied in the x-axis direction and in the y-axis direction via the electrodes 241, 242, 243 and 244 that are provided at end portions of the four sides of the transparent conductor layer 240 as illustrated in FIG. 4A. When the transparent conductor layers 230 and 240 make contact at contact positions A and B that are pressed simultaneously by the finger tips F of the user, for example, a potential Vc is detected via the transparent conductor layer 230 as illustrated in FIG. 4B, in order to detect coordinate positions in the x-axis direction and the y-axis direction. In this case, an intermediate position between the contact positions A and B is detected from the potential Vc, even though the two contact positions A and B are pressed and the intermediate position is not pressed. In other words, the intermediate position between the contact positions A and B is erroneously detected when the two contact positions A and B are pressed simultaneously.